San Francisco (12-12) 17:29 PST -- Thanks to a Chronicle story and a bighearted donor, families of San Francisco schoolchildren now living on the street will have a home for the holidays.

As many as 200 families spending their nights in city shelters, sleeping in cars or on the streets will be moved into public or subsidized housing, with many of them in their new homes by Christmas, said Mayor Ed Lee. The $3 million for the program will come from city money and a $1.5 million contribution from Marc and Lynne Benioff of Salesforce.com, a fast-growing San Francisco tech company.

Lynne Benioff said as soon as she read the Dec. 4 Chronicle story about the plight of the growing number of homeless children in the city's public schools, she knew something had to be done.

"Marc and I saw this as an emergency, affecting children's health, so we reached out to the mayor's office," Lynne Benioff said. "We thought we could probably help the city do something about this."

Lee and city staffers knew all about the problem and had been working on ways to deal with it. The problem, as always, was finding the needed money.

"We got a huge bump with Lynne Benioff calling and saying she wanted to help," the mayor said. "We immediately knew that we wanted to get as many families as possible in homes before Christmas."

Lynne Benioff cheerfully admitted that she and her husband, the founder and CEO of Salesforce, challenged the city to move the people into housing for the holidays.

Within 24 hours, the city and the Benioffs had reached an agreement to jump-start the program to help the schoolkids.

The city and the school district have different definitions of who qualifies as homeless, which means their numbers don't always mesh. While school officials report that nearly 2,200 of their students are homeless, nearly 1,000 of them are living in single-room-occupancy hotels or other situations that don't meet the city's criteria, said Malcolm Yeung, an aide to the mayor for housing matters.

The city has 79 families in long-term city shelters and an additional 253 on the waiting list for those rooms. Because children in public schools will have priority under the new program, moving 200 of those families into regular housing will help a significant percentage of the city's homeless schoolchildren.

About 30 or 40 families will be able to immediately move into vacant public housing units, said Yeung, while an additional 160 or 165 will receive assistance finding subsidized private rental units.

The Benioffs will donate their $1.5 million to their choice of community-based organizations, which will help families find housing and provide up to 18 months of rent assistance. The organizations also will provide assistance to the families, working to help them get in a position to move into non-subsidized housing, Yeung said.

For Lee, the program is an example of how the city can work in partnership with private companies to deal with San Francisco's problems.

"Quite frankly, we want others to help, we want other companies to join in," the mayor said. "The Benioffs are part of the leadership of the new companies that are going to be our philanthropic leaders in the 21st century.

This isn't the first time the Benioffs have stepped up for children's health. Last year, the couple committed $100 million toward a new children's hospital at UCSF's new site at Mission Bay, where Salesforce will be building its corporate headquarters.

A City Hall hearing this morning, called by Supervisor John Avalos, will look at the dramatic rise of family homelessness in the city. Members of the Coalition on Homelessness and other housing advocates have called on the city to make a concerted effort to help families now in shelters and on the streets as the winter cold sets in.